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Chemistry ⚗ > Chapter 15 > Flashcards

Chapter 15 Flashcards

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1
Q

what is corrosion caused by?

A

chemical reactions between the metal and the chemicals in the environment

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2
Q

what is rusting?

A

the corrosion of iron

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3
Q

what two conditions are needed for iron to rust?

A

oxygen and water

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4
Q

why does the mass of iron increase as it rusts?

A

the atoms bond with the oxygen and water molecules, which makes a compound that is heavier than iron

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5
Q

equation for the rusting of iron III

A

iron + oxygen + water -> hydrated iron (III) oxide

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6
Q

what happens to the iron when it rusts?

A

it is oxidised

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7
Q

3 ways of barriers to stop rusting

A

paint
oil/grease
plastic

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8
Q

what is the sacrificial method of preventing rusting?

A

a more reactive metal is placed onto the iron so the iron stays intact

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9
Q

what happens when iron is galvanised?

A

it is covered with a layer of zinc so the oxygen and water oxidise and react with zinc, not iron

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10
Q

why isn’t aluminium completely destroyed by corrosion?

A

aluminium oxide forms a protective layer that stops any further reactions taking place

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11
Q

why is iron completely destroyed by rusting?

A

iron oxide is flaky and will fall off to leave more iron exposed to react again

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12
Q

what is an alloy?

A

a mixture of a metal and another material

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13
Q

why are alloys much harder than normal metals?

A

the structure of the metal is disrupted so the layers can’t slide over eachother

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14
Q

what is bronze made from?

A

copper + tin

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15
Q

why is bronze better than copper?

A

it is much harder

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16
Q

uses of bronze 3

A

make medals, decorative ornaments and statues

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17
Q

what is brass made from?

A

copper + zinc

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18
Q

why is brass better than bronze?

A

it is more malleable and is used where there needs to be little friction

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19
Q

uses of brass 3

A

musical instruments, taps, door fittings

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20
Q

what is the most useful property of aluminium?

A

its low density

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21
Q

why is aluminium alloyed?

A

to make it stronger

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22
Q

uses of aluminium alloys 2

A

aircraft

plating on military vehicles

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23
Q

why is gold alloyed?

A

to make it stronger

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24
Q

why is copper mixed with gold?

A

it is more long wearing

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25
Q

uses of gold alloys

A

jewellery

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26
Q

what is 24 carat gold?

A

pure gold

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27
Q

how to work out how much gold is in a carat?

A

divide number by 24

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28
Q

what are steels?

A

alloys of iron with carbon and other elements

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29
Q

what are the simplest steels?

A

carbon steels

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30
Q

how are carbon steels made?

A

most of the carbon is removed is removed from the iron

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31
Q

uses of carbon steels 3

A

car bodies
ships
structural steel

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32
Q

properties of high carbon steels 2

A

strong but brittle

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33
Q

properties of low carbon steels 2

A

soft and easily shaped

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34
Q

what are nickel-steel alloys used for and why?

A

long-span bridges, bicycle chains

resistant to stretching forces

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35
Q

what is stainless steel made from?

A

chromium and nickel

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36
Q

characteristics of stainless steel? 2

A

don’t rust

very strong

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37
Q

uses of stainless steels

A

cutlery, cooking utensils,

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38
Q

what do the properties of a polymer depend on?

A

the monomers used to make it

the conditions under which the reaction happened

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39
Q

what are the two types of polyethene?

A

low density polyethene

high density polyethene

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40
Q

how is low density polyethene made?

A

very high temperatures and a catalyst

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41
Q

what is LD polyethene used for and why?

A

plastic bags and bottles

it is very flexible

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42
Q

what gives LD polyethene its low density?

A

the polymer chains are randomly branched and can’t pack closely together

43
Q

how is HD polyethene made?

A

lower temperature (50c) and a different catalyst(

44
Q

use of LD polyethene and why

A

water tanks

it is very rigid

45
Q

what gives HD polyethene its high density?

A

the polyethene chains are straighter and can pack together more closely

46
Q

what are thermosetting polymers?

A

they don’t soften when heated because of the ‘cross links’ between polymer chains

47
Q

what are thermosoftening polymers?

A

they soften when heated

made of individual polymer chains tangled together

48
Q

what allows thermosoftening polymers to soften under heat?

A

weak intermolecular forces between the polymer chains that need little energy to overcome
when it cools, the forces bring the polymer back together again

49
Q

what stops thermosetting polymers from softening under heat?

A

the monomers form covalent ‘cross links’ between polymer chains which are strong and won’t soften

50
Q

what is glass mainly made from?

A

sand

51
Q

how is glass made?

A

the raw materials (sand, limestone and sodium carbonate) are heated to 1500c
they melt and react to form molten glass
when they cool, they remain in this disorganised structure

52
Q

how to make different types of glass

A

use different raw materials

53
Q

what is different about borosilicate glass and what is it used for?

A

it has boron trioxide in it

it is used for oven ware as it has a high melting point

54
Q

what are ceramics?

A

non metal solids with high melting points that aren’t made from carbon based compounds

55
Q

examples of ceramics made form clay 3

A

bricks, crockery and toilets

56
Q

how are clay ceramics made?

A

wet clay is moulded into desired shape and heated at 1000c

57
Q

why do the properties of clay change so drastically when heated?

A

there is ionic bonding between metals and non metals in clay
covalent bonding between non metals
arranged in giant layers
when wet, water gets between layers and makes them slimy
when they are heated, water is driven out and strong bonds form between layers

58
Q

what are composites made from?

A

one material embedded in another

59
Q

4 examples of composites

A

fibreglass
carbon fibre
concrete
wood

60
Q

why is natural wood so strong?

A

cellulose

61
Q

what is a matrix in a composite?

A

it acts as a binder and holds everything together

62
Q

what is fibreglass made from?

A

fibres of glass embedded in a matrix made of plastic

63
Q

properties of fibreglass 2

A

low density

very strong

64
Q

what is fibreglass used for? 3

A

skis
boats
surfboards

65
Q

what is concrete made from?

A

aggregate (sand and gravel) embedded in cement

66
Q

use of concrete

A

building materials

67
Q

what is carbon fibre made from?

A

long chains of carbon atoms in plastic

carbon nanotubes in plastic

68
Q

use of carbon fibres

A

aerospace

sports car manufacturing

69
Q

what do most fertilisers contain?

A

nitrogen, phosphorous and potassium

70
Q

why do fertilisers contain nitrogen and similar nutrients

A

crops grow and absorb nutrients for growth
farmers harvest plants, so little of the plant is allowed to decompose and add nutrients back to the soil
so farmers have to replace the missing nutrients or provide more of them

71
Q

even though there is a lot of nitrogen in the air, why don’t plants absorb it?

A

the gas is insoluble in water and plants can only absorb a soluble form of nitrogen

72
Q

what is the haber process?

A

nitrogen and hydrogen are converted to ammonia, which is used in fertilisers

73
Q

who created the haber process?

A

german scientist Fritz haber

74
Q

what is the most important use of ammonia?

A

fertilisers

75
Q

how is the nitrogen for the Haber process sourced?

A

obtained from the air

76
Q

how is hydrogen sourced for the Haber process?

A

methane is reacted with steam to form hydrogen and carbon dioxide

77
Q

what are the three conditions used in the haber process?

A 
iron catalyst
high pressure (200 atmospheres)
high temperature (450c)
78
Q

the Haber process:

A

nitrogen and methane are sourced
they are passed over an iron catalyst at high temperature and pressure
this reaction is reversible so some ammonia formed is converted back to the raw materials
a dynamic equilibrium is reached
ammonia formed as a gas
it is collected, condensed and turned into fertiliser
the unused reactants are recycled so nothing is wasted

79
Q

how is ammonia obtained from the Haber process?

A

the gases are cooled

ammonia liquefies and can be separated

80
Q

equation for haber process

A

nitrogen + hydrogen (half arrows) ammonia (+ heat)

N2 + 3H2 (half arrows) 2NH2 (+ heat)

81
Q

equation for the formation of hydrogen

A

methane + steam -> hydrogen + carbon dioxide

82
Q

why are fertilisers used?

A

replace missing nutrients
increases crop yield
crops grow faster and bigger

83
Q

how to create ammonia nitrate

A

ammonia + nitric acid

84
Q

how is ammonia phosphate formed?

A

ammonia + phosphoric acid

85
Q

when are salts formed?

A

when acids and alkalis react together in a neutralisation reaction

86
Q

is ammonia solution alkali or acid

A

alkali

87
Q

how is ammonium nitrate formed in industry?

A

in giant vats
high concentrations
very exothermic reaction
the heat released evaporates water, leaving a very concentrated ammonium nitrate product

88
Q

how is ammonium nitrate formed in the lab?

A 
smaller scale
titration and crystallisation
reactants are at a lower concentration
less heat produced
after titration, the solution is crystallised to result in pure ammonium nitrate crystals
89
Q

why is crystllisation not used in industry?

A

it is too slow

90
Q

how to make ammonium sulfate?

A

react ammonia with sulfuric acid

91
Q

what is NPK fertiliser?

A

Nitrogen, phosphorous and potassium fertiliser

92
Q

where to source phosphorous?

A

rocks

93
Q

why is acid added to phosphorous rocks?

A

plants can’t use it as it is insoluble in water

94
Q

what is produced when phosphate rock is reacted with nitric acid?

A

phosphoric acid and calcium nitrate

95
Q

what is produced when phosphate rock is reacted with sulfuric acid?

A

calcium sulfate and calcuim phosphate

also known as single superphosphate

96
Q

what is produced when phosphate rock is reacted with phosphoric acid?

A

tripe superphosphate

97
Q

how is nitrogen obtained from air?

A

air is cooled to -200c to liquefy it

fractional distillation happens

98
Q

reaction for methane + steam

A

methane + steam -> hydrogen + carbon monoxide

99
Q

what is the main cost of producing ammonia?

A

sourcing the methane, which is a natural gas

100
Q

why is 200 atmospheres of pressure used?

A

there are less moles of ammonia than reactants
so, higher pressure = higher yield
but, higher pressure is also expensive and dangerous
so 200 atmospheres is a compromise

101
Q

why is an iron catalyst used?

A

it speeds up both the forward and reverse reaction

doesn’t affect yield of ammonia but makes it be produced quicker

102
Q

what is the forward reaction of the production of ammonia?

A

exothermic

103
Q

why is 450c used for the Haber process?

A

forward reaction is exothermic
increasing temperature = less yield
but decreasing temperature = slower rate of reaction and minimises effect of catalyst
450c is a compromise between maximum yield and speed of reaction

Chemistry ⚗ (17 decks)

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